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To improve the flame retardancy of low‐density polyethylene (LDPE) and mechanical properties of LDPE composites, phenol‐formaldehyde aluminum diethylphosphinate microcapsules (PF@ADP) was prepared by in‐situ polymerization with phenol‐formaldehyde (PF) resin as the wall material and halogen‐free flame‐retardant aluminum diethylphosphinate (ADP) as the core material. The effects of PF@ADP on flame retardancy and mechanical properties of LDPE were investigated by methods of combustion experiments, mechanical analysis, thermogravimetric analysis (TGA), and smoke density analysis. The results indicated that, compared with ADP/LDPE composites, the flame retardancy and mechanical properties of PF@ADP/LDPE were obviously improved. With the addition of 20 wt% PF@ADP (PF:ADP = 3:7), the limit oxygen index (LOI) of LDPE composites increased to 30.7% and UL‐94 reached V‐1 grade. The tensile strength and elongation at break reached 12.5 MPa and 431.2%, which was 20.2% and 23.1% higher than that of ADP/LDPE with the same addition. The addition of PF@ADP was beneficial to the smoke suppression of LDPE.

To improve the flame‐retardant property of low‐density polyethylene (LDPE) composites, a novel intumescent flame retardant (IFR) consisting of ammonium polyphosphate (APP) covered by silicon dioxide and 3‐(Methylacryloxyl) propyltrimethoxy silane (KH‐570) (SiO2@MAPP) and double pentaerythritol (DPER) was synthesized. Various methods were applied to structural characterization and property investigations of different samples. The results indicated that the solubility of APP decreased after coating with silicon dioxide (SiO2) and KH‐570. The flame retardancy of LDPE composites was improved with addition of IFR containing SiO2@MAPP/DPER. With 30 wt% addition of IFR containing SiO2@MAPP /DPER, the limiting oxygen index reached 26.8% and the tensile strength was 3.30 MPa. The tensile strength was 7.14% higher than that of 30 wt% IFR without SiO2@MAPP. The smoke density test showed that the flue gas emission was obviously improved. The addition of SiO2@MAPP effectively increased the residual carbon content of composites and thermal stability of the composites.

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Purpose The purpose of this study is to investigate the effect of chlorination on the structure and properties of reclaimed rubber and to discuss the feasibility of a novel method to chlorinate reclaimed rubber. Design/methodology/approach A series of chlorinated reclaimed rubber with different chlorination degrees (CD) was prepared by suspension chlorination in aqueous phase (SCAP). Their structure and performance were characterized by Fourier transform infrared spectrometer, energy dispersive spectroscopy, scanning electron microscopy, thermogravimetric and mechanical property test. Findings The chemistry structure, mechanical performance and heat resistance of CRR is affected greatly by its CD. Research limitations/implications Although in the present work only chlorination of reclaimed rubber is researched, but this method can be used to modify other recycled rubber. Practical implications SCAP is a useful method to produce CRR, and it is feasible for production of chlorinated recycled rubber in large scale. The present work provides a new strategy to fabricate new materials based on recycled rubber. Social implications Chlorination of reclaimed rubber by SCAP is useful to convert waste rubber into new materials, and it is useful to decrease environment pollution. Originality/value SCAP method provides a new technology to chlorinate waste rubber with many merits, such as chlorination rate of RR is accelerated and the reaction can be controlled or adjusted easily. Moreover, conversion of chlorine is increased remarkably.